This invention relates to a feeding mechanism for fastener driving devices and more particularly to fastening devices used in continuous production lines having a feeding mechanism for feeding successive fasteners into the drive track of the device.
Conventional staple feeding mechanisms must perform the task of feeding and holding the staples in the drive track. In certain devices, sticks of staples are loaded onto a magazine that is angled downward so that the force of gravity aids in pulling the staples down to the nose of the device and into the drive track. However, the force of gravity alone is insufficient to feed and hold the staples in the drive track.
To increase the force on the staples at the nose of the device, a mechanism has been used including a friction clutch and a wheel connected to an electric motor. Thus, as the motor turns, the clutch maintains a certain torque on the wheel which in turn keeps a constant forward force on the staples. When a staple is driven, the remaining staples are fed and held forward toward the drive track. Other conventional feed mechanisms use a ratchet to hold and feed staples to the drive track. The feed is made under spring pressure and the cycling action for the feed stroke comes during the power stroke of the device. It is common to connect the return piston to a source of air under pressure which is communicated in response to the actuation of the device. Consequently, instead of feeding during the drive stroke, the conventional ratchet is recycling or retracting during the drive stroke and the fastener which has already been fed into the drive track is held therein by a holding pawl. Although these type of feed mechanisms work well for their intended purpose, they typically require an extra power source to be connected to the device, and are inefficient and expensive.
Other conventional feed mechanisms employ a spring biased pusher which contacts the rearmost staple of the staple stick urging the staples forward along a guide to the drive track. The devices are effective in feeding and holding the staples in the drive track of the device, however, when a staple stick has been exhausted, the pusher must be retracted to allow another staple stick to be placed on the guide. In a continuous production line such interruptions can be disruptive and costly due to lost productivity.